1. Field of the Invention
The present invention relates to a computer system having a main body and an expansion unit attached to/detached from the main body. More particularly, it relates to a computer system in which an expansion unit can be attached and detached in the main body which power is being supplied to the main body.
The invention also relates to a computer system which has a main body and an expansion unit driven by using the battery provided in the main body and in which the main body and the expansion unit can be connected to a connector having a small number of pins.
2. Description of the Related Art
In recent years, various personal portable computers of a laptop type and a notebook type easily carried and operable by a battery have been developed. The portable computer of this type is constructed such that an expansion unit can be attached so as to expand its functions, as necessary.
The expansion unit has a drive bay housing driving devices such as a hard disk drive and the like, and expansion slots through which various optional cards are placed. Therefore, by using the portable computer connected to this expansion unit as necessary, it is possible to easily expand the functions of the portable computer without losing its portability.
Recently, moreover, expansion units as a simple type expansion unit, for example a port replicator incorporating a PC card controller, have been developed. Thus, depending on purposes, the same portable computer is used being selectively connected to a plurality of expansion units.
Conventionally, while the power of the computer main body is turned ON, attaching and detaching of the expansion unit have involved the risk of destroying the optional card of the expansion unit, because of unexpected flowing of a current from the computer main body to the optional card due to hot swapping. As a result, it is necessary for a user manually that the power of the expansion unit and the main body is turned off, prior to attaching and detaching the main body to and from the expansion unit. The conventional type thus has a lack of convenience.
Where the portable replicator incorporating PC card controller is used, conventionally three kinds of driving power sources, 3.3V, 5V and 12V have all been supplied from the main body to PCMCIA slots. As a result, the number of pins used as power lines increase and the size of the connector, for connecting the computer main body with the expansion unit, increase. Also, power is always output into the connector in the main body side. Thus, if no expansion units are placed, the pins of the connector may be short-circuited for some reason, allowing an excessive current to flow. This excessive current may damage devices within the main body.
In the main body and the expansion unit, a connector for connecting such peripheral equipment as a mouse, a keyboard, a joystick and the like therewith is provided. Power is supplied from the main body to the peripheral equipment by this connector. A fuse is normally connected to a line for supplying power for the purpose of protection from an excessive current.
In such a method using the fuse, however, when the fuse is blown and needs to be replaced, the main body must be sent to a service center, etc., for repair. This is usually for the reason that it is far more difficult for the user to repair the portable computer of the notebook type and the like, than a desktop type. In order to deal with this problem, use of excessive current protection parts of automatic recovery type, for instance a breaker, may be considered. Being large in size, however, it is difficult for these to be actually used in the portable computer.
As described above, the expansion unit is important in order to expand the functions of the portable computer. Conventionally, however, attaching and detaching of the computer main body to and from the expansion unit, while power for the computer main body is turned ON, has resulted in destruction of the optional card and the computer hanging-up. There has also been a problem of supplying of a number of power lines from the main body to the expansion unit. Furthermore, in the conventional type, the fuse has been used for the purpose of protection from an excessive current and the main body must be sent for repair when the fuse is to be replaced.